The use and mechanism of control agents for free radical polymerization is now generally known, see for example WO98/01478, WO99/35177, WO99/31144, and WO98/58974, each of which is incorporated herein by reference. Despite this knowledge, no successful commercialization of a polymerization process has occurred with these agents. Thus the need for new agents, which lead to a commercializable process are needed.
In addition, the previously known control agents have limited uses. Although touted as universally useful, those of skill in the art appreciate that a particular control agent is particularly useful for the control of particular monomers and monomer mixtures. The polymerization conditions under which particular control agents are particularly useful are generally not well known. Thus, a need exists for a family of related control agents that can be easily synthesized and modified so that a control agent will be readily available for polymerizing desired monomers under commercially acceptable conditions, which include high conversion at the shortest possible reaction times and lower temperatures.
This invention solves these issues by providing control agents that can be easily modified for particular monomers and monomer mixtures. The control agents of the present invention contain at least one nitrogen—nitrogen bond, which allows for simpler modification of the electronic and steric nature of the control agents as compared to known control agents. These modified properties allow for improved conditions of the polymerization process and/or improved properties of the polymers obtained from the processes.